Organic el display device and manufacturing method for organic el display device

ABSTRACT

This organic-EL display apparatus comprises: a substrate with a drive circuit comprising a thin-film transistor (TFT), a planarizing layer to cover the drive circuit, and an organic light-emitting element formed upon the surface of the planarizing layer facing the opposite direction from the drive circuit. The TFT comprises a drain electrode, a source electrode, and a semiconductor layer that includes regions to be a channel of TFT and partially overlaps with the source and drain electrodes. Respective parts of a first conductor layer forming the drain electrode and a second conductor layer forming the source electrode are arranged in an alternating manner along a prescribed direction, and the region to be the channel is sandwiched between the part of the first conductor layer and the part of the second conductor layer.

TECHNICAL FIELD

The present invention relates to an organic-EL display apparatus and amethod of manufacturing an organic-EL display apparatus.

BACKGROUND ART

An organic-EL display apparatus, application of which organic-EL displayapparatus to a television is in progress in recent years, comprises anorganic light-emitting element being formed for each pixel, and a drivecircuit to cause the organic light-emitting element to emit light with adesired current. In an active matrix-type organic-EL display apparatus,a thin-film transistor making up the drive circuit is formed on asurface of a glass substrate for each pixel to be provided in a matrix,and an organic light-emitting element is formed on an insulating layercovering the thin-film transistor. Patent document 1 discloses forming athin-film transistor that has a multilayer structure in order to reducethe occupied area of the thin-film transistor relative to the pixel insuch an active matrix-type display.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: JP 2017-011173 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In an organic-EL display apparatus, an organic light-emitting element isa current drive-type light-emitting element, so that the current supplycapability (the drive capability) being higher than that in a liquidcrystal display apparatus is required for a drive circuit for theorganic light-emitting element. While the drive capability can beenhanced by making a thin-film transistor to have a deposition structureas in Patent document 1, the manufacturing cost inevitably increases.However, for further popularization of an organic-EL display panel intoa large-sized television, a further improvement in the drive capabilityof the drive circuit and a substantial reduction in manufacturing costare desired. Moreover, in the organic-EL display panel, when luminancenon-uniformity or color non-uniformity (below, “luminance non-uniformityand/or color non-uniformity” also collectively called “displaynon-uniformity”) occurs, the product value of the organic-EL displaypanel deteriorates. Such a display non-uniformity being likely to beconspicuous in a larger screen could prevent the popularization of theorganic-EL display panel. While a compensation circuit for the displaynon-uniformity is being provided, or a correction unit is provided tocorrect a drive current of the organic light-emitting element afterobserving the initial display state, taking such measures also causes anincrease in size or cost.

Thus, an object of the present invention is to provide an organic-ELdisplay apparatus making it possible to enhance the capability of adrive circuit with a structure also allowing cost reduction and, evenmore, having a small display non-uniformity, and to provide a method ofmanufacturing an organic-EL display apparatus allowing to suitablymanufacture the organic-EL display apparatus having a drive circuitbeing excellent in drive capability and having a small displaynon-uniformity as such.

Means to Solve the Problem

An organic-EL display apparatus according to first embodiment of thepresent invention comprises: a substrate having a surface with a drivecircuit formed on the surface, the drive circuit comprising a thin-filmtransistor; a planarizing layer to planarize the surface of thesubstrate by covering the drive circuit; and an organic light-emittingelement being formed on a surface of the planarizing layer facing to anopposite orientation from the drive circuit, and electrically connectedto the drive circuit, wherein the surface of the planarizing layer hasan arithmetic average roughness of 50 nm or less; the thin-filmtransistor comprises a gate electrode, a drain electrode, a sourceelectrode, and a semiconductor layer comprising a region to be a channelof the thin-film transistor and partially overlapping with the drainelectrode and the source electrode; a part of a first conductor layermaking up the drain electrode and a part of a second conductor layermaking up the source electrode are alternately lined up along a givendirection; and the region to be a channel is sandwiched between the partof the first conductor layer and the part of the second conductor layer.

A method of manufacturing an organic-EL display apparatus according tosecond embodiment of the present invention comprises: forming a drivecircuit on a substrate, the drive circuit comprising a thin-filmtransistor; forming, on a surface of the drive circuit, a firstinorganic insulating layer, an organic insulating layer, and a secondinorganic insulating layer; polishing a surface of the second inorganicinsulating layer; forming a contact hole in the second inorganicinsulating layer, the organic insulating layer, and the first inorganicinsulating layer, so as to reach the thin-film transistor; embedding ametal at the interior of the contact hole and forming a first electrodeat a given region; forming an organic light-emitting layer on the firstelectrode; and forming a second electrode on the organic light-emittinglayer, wherein the thin-film transistor is formed so as to have adeposition structure comprising a gate electrode, a gate insulatinglayer, a semiconductor layer comprising a region to be a channel, afirst conductor layer making up a drain electrode, and a secondconductor layer making up a source electrode; the first conductor layerand the second conductor layer are formed such that a part of the firstconductor layer and a part of the second conductor layer are alternatelylined up along a given direction; and the region to be a channel issandwiched between the part of the first conductor layer and the part ofthe second conductor layer.

Effects of the Invention

The first embodiment of the present invention makes it possible toenhance the capability of a drive circuit with a structure also allowingrealization of cost reduction and, even more, to reduce displaynon-uniformity in an organic-EL display apparatus. Moreover, the secondembodiment of the present invention makes it possible to suitablymanufacture an organic-EL display apparatus having a drive circuit beingexcellent in drive capability and having a small display non-uniformityas such.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows one example of a drive circuit of anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 2A schematically shows a cross sectional view of one example of anorganic light-emitting element and a thin-film transistor of theorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 2B schematically shows a cross sectional view of another example ofthe thin-film transistor of the organic-EL display apparatus accordingto one embodiment of the present invention.

FIG. 2C schematically shows a cross sectional view of yet anotherexample of the thin-film transistor of the organic-EL display apparatusaccording to one embodiment of the present invention.

FIG. 3A shows a plan view of one example of each electrode of thethin-film transistor of the organic-EL display apparatus according toone embodiment of the present invention.

FIG. 3B shows a plan view of another example of each electrode of thethin-film transistor of the organic-EL display apparatus according toone embodiment of the present invention.

FIG. 3C shows a plan view of yet another example of each electrode ofthe thin-film transistor of the organic-EL display apparatus accordingto one embodiment of the present invention.

FIG. 4A shows a cross-sectional view of one example of the thin-filmtransistor of the organic-EL display apparatus according to oneembodiment of the present invention.

FIG. 4B shows a cross-sectional view of another example of the thin-filmtransistor of the organic-EL display apparatus according to oneembodiment of the present invention.

FIG. 5A shows a flowchart of a method of manufacturing an organic-ELdisplay apparatus according to one embodiment of the present invention.

FIG. 5B shows a flowchart on a process of forming the drive circuit inFIG. 5A.

FIG. 6A is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6B is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6C is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6D is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6E is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6F is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

FIG. 6G is a cross sectional view showing the method of manufacturing anorganic-EL display apparatus according to one embodiment of the presentinvention.

EMBODIMENT FOR CARRYING OUT THE INVENTION

The present inventors have carried out intensive studies to enhance thedrive capability of a drive circuit. Then, the present inventors havefound that forming a drain electrode and a source electrode of athin-film transistor making up the drive circuit such that a part of thedrain electrode and a part of the source electrode are lined up along agiven direction makes it possible to substantially enhance the drivecapability and, even more, to form the drive circuit within a region forone pixel of an organic-EL display apparatus. In other words, formingthe drain electrode and the source electrode in this way makes itpossible to increase a length (a channel width (W)) of a portion atwhich both of the electrodes face each other, without increasing aninterval (a channel length (L)) between the drain electrode and thesource electrode. Therefore, the ratio (W/L) of the channel width andthe channel length can be increased substantially and, even more,efficiently in a given compartment and, as a result, a drive circuithaving a substantially enhanced drive capability can be laid out in onepixel.

Moreover, the present inventors have found that using such a structurefor the thin-film transistor makes it possible to form a semiconductorlayer to be a channel of the thin-film transistor making up the drivecircuit of the organic-EL display apparatus using not polysilicon (inparticular, low temperature polysilicon: LTPS) but amorphous silicon. Inother words, the LTPS being excellent in terms of carrier mobility hasbeen used conventionally for a semiconductor layer of such a thin-filmtransistor. However, the present inventors have found that applying theconfiguration of each of the electrodes described previously enableseven the semiconductor layer made of amorphous silicon to functionadequately in the drive circuit of the organic-EL display apparatus.

LTPS is obtained by forming a semiconductor layer of amorphous siliconand, thereafter, carrying out annealing for the amorphous silicon byirradiating an excimer laser, thereby poly-crystallizing the amorphoussilicon. This complicates the manufacturing process and the annealingprocess prevents a reduction in manufacturing cost of the organic-ELdisplay panel. Moreover, facilities required for irradiating the excimerlaser are extremely expensive and, even more, the realization offacilities that can be applied to a mother substrate being in excess ofthe tenth generation as already introduced in a manufacturing line of aliquid crystal display apparatus is not foreseen. Furthermore,irradiating the excimer laser uniformly on the entire surface of thesubstrate on which the drive circuit is formed is extremely difficult,so that variations in carrier mobility occur easily and substantiallyamong each of a plurality of LTPSs, each of which is poly-crystallizedin each given compartment on the substrate, possibly causing, as aresult, variations in, for example, gate threshold voltage to occureasily among each of the thin-film transistors. Irradiating the excimerlaser uniformly on the mother substrate will be increasingly difficultwith upsizing of the mother substrate. The present inventors have foundthat using the previously-described structure of the thin-filmtransistor makes it possible to form the semiconductor layer of thethin-film transistor in the drive circuit of an organic-EL display panelwith amorphous silicon not requiring annealing.

The present inventors have further found that unevenness of the surfaceof the drive circuit being formed on the surface of the substrateproduces variations in layer thickness of an organic layer in an organiclight-emitting element, possibly producing, as a result, luminancenon-uniformity or color non-uniformity. Describing in further detail, aninsulating layer is provided between the drive circuit and the organiclight-emitting element as described previously, and the insulating layermakes it possible to achieve planarization of the base for the organiclight-emitting element as well as blocking of moisture and electricalisolation of the drive circuit and the organic light-emitting element.However, the present inventors have found that the planarization is notnecessarily sufficient from a viewpoint that an excellent displayquality can be obtained. In a case that the surface of such aninsulating layer (a planarizing layer) is not sufficiently planar, avariation in layer thickness of an organic layer formed on the surfaceof the insulating layer via an electrode causes luminance non-uniformityand/or deviation of a direction in which an outgoing light has its peakintensity from the normal direction of the display surface, therebycausing the display non-uniformity. The present inventors have foundthat occurrence of the display non-uniformity can be suppressed byachieving further planarization of the surface of the planarizing layerto be the base for the organic light-emitting element. Moreover,achieving further planarization of the surface of the planarizing layeras such makes it possible to suppress, even in a case that the thin-filmtransistor having the structure as described previously is formed at anunderlayer of a light-emitting region of the organic light-emittingelement, the display non-uniformity that can be produced due to theunevenness on the surface of the planarizing layer.

Below, an organic-EL display apparatus and a method of manufacturing anorganic-EL display apparatus according to embodiments of the presentinvention are described with reference to the drawings. Material andshape of individual constituting elements, and relative positionalrelationship thereof in the embodiments to be described below are merelyexemplary. The organic-EL display apparatus and method of manufacturingan organic-EL display apparatus according to the present invention areconstrued to be not limited thereto.

(Organic-EL Display Apparatus)

In FIG. 1, one example of a configuration of a drive circuit 2 of anorganic-EL display apparatus 1 according to first embodiment is showntogether with an organic-EL display panel 3, a data line driver 1 d, anda scanning line driver 1 g, each of which is shown schematically. Theorganic-EL display panel 3 comprises a plurality of pixels 3 a beingarranged in a matrix, and an organic light-emitting element 40 and thedrive circuit 2 are provided in each of the pixels 3 a. In the examplein FIG. 1, the drive circuit 2 comprises a driving TFT 20 to switch theconduction state of the organic light-emitting element 40, a switchingTFT 2 a to switch on/off of the driving TFT 20, and a storagecapacitance 2 b to hold the gate-source voltage of the driving TFT 20.The drain, the source, and the gate of the driving TFT 20 are connectedto a power line 2 p, an anode of the organic light-emitting element 40,and the source of the switching TFT 2 a, respectively, while a cathodeof the organic light-emitting element 40 is connected to the ground viaa cathode wiring 27.

A gate signal is transmitted to the individual switching TFT 2 a fromthe scanning line driver 1 g and also a data signal of a display imageis applied to the gate of each driving TFT 20 via the individualswitching TFT 2 a from the data line driver 1 d. A current based on thevoltage of the data signal flows to the organic light-emitting element40, and the organic light-emitting element 40 emits light at a givenluminance during one frame period thanks to the behavior of the storagecapacitance 2 b. Below, the organic-EL display apparatus 1 according tothe present embodiment is explained with reference to FIGS. 2A to 2Cshowing cross sections of the organic-EL display panel 3 and includingone of the pixels 3 a. In the explanations below, the driving TFT 20 ismerely called “the thin-film transistor 20 (TFT 20)”. Moreover, the“pixel” being referred to in the explanations and each of the drawingsin the above and in the following is a minimum constituting element(unit element) of a display screen, to be exact, “a sub-pixel”, but isalso called a “pixel” for brevity of explanations. Furthermore, the“surface” in the explanations in the following means a surface facing toan opposite orientation from a substrate 10 (see FIG. 2A) in eachconstituting element constituting the organic-EL display apparatus 1other than the substrate 10 in a case that no distinction thereof isparticularly recited. Moreover, the “surface” with respect to thesubstrate 10 means a surface facing to the organic light-emittingelement 40 in a case that no distinction thereof is particularlyrecited.

A structure of the TFT 20 of the drive circuit 2 of the organic-ELdisplay apparatus 1 according to the present embodiment is explainedwith reference to FIGS. 2A to 2C and FIGS. 3A to 3C. FIGS. 2A to 2Cshows, in an enlarged manner, a cross section of the organic-EL displaypanel 3, and, particularly, one example of a cross section of the TFT 20and the organic light-emitting element 40. FIGS. 3A to 3C each show aplan view of a specific example of the TFT 20 (a drain electrode 26 anda source electrode 25 are hatched.) FIGS. 2A to 2C show, as the TFT 20,a cross section of one of a plurality of portions at which a part of thesource electrode 25 and a part of the drain electrode 26 face each other(a cross section along a cutting line being along the opposing directionof both electrodes or along the Y direction in FIG. 3A, for example, isshown). Moreover, while FIGS. 2A to 2C show a gate electrode 23 and ansemiconductor layer 21 as being formed only in a facing portion of thesource electrode 25 and the drain electrode 26, the gate electrode 23can be formed such that it extends over the entirety of the plurality offacing portions of the source electrode 25 and the drain electrode 26.

As shown in FIGS. 2A to 2C, the organic-EL display apparatus 1 accordingto the present embodiment comprises a substrate 10 having a surface onwhich the drive circuit 2 comprising the TFT 20 has been formed; aplanarizing layer 30 to planarize the surface of the substrate 10 bycovering the drive circuit 2; and the organic light-emitting element 40being formed on a surface of the planarizing layer 30 facing to anopposite orientation from the drive circuit 2, and electricallyconnected to the drive circuit 2. The TFT 20 comprises the gateelectrode 23, the drain electrode 26, the source electrode 25, and asemiconductor layer 21 comprising a region to be a channel 21 c of theTFT 20. The semiconductor layer 21 partially overlaps with the drainelectrode 26 and the source electrode 25. In the example in FIG. 2A, asecond semiconductor layer 211 formed of a semiconductor having a highimpurity concentration is provided between the semiconductor layer 21and each of the drain electrode 26 and the source electrode 25. Achannel is formed by applying a given voltage to the gate electrode 23mainly at a region 21 c in the semiconductor layer 21. The region 21 cis a region between the drain electrode 26 and the source electrode 25,and overlaps with the gate electrode 23.

FIG. 2A shows an example of a bottom gate structure (reverse-staggeredstructure) in which the gate electrode 23 is arranged between thesemiconductor layer 21 and the substrate 10, while FIG. 2B shows anexample of a top gate structure (staggered structure). FIGS. 2A and 2Bshow an example in which the semiconductor layer 21 is made of amorphoussilicon. Moreover, FIG. 2C is an example of the TFT 20 having the topgate structure in the same manner as the example in FIG. 2B. Thestructure exemplified in FIG. 2C is used mainly in a case that theregion to be a channel 21 c of the semiconductor layer 21 is formed ofLTPS. While the drive circuit 2 of the organic-EL display apparatus 1according to the present embodiment is preferable in a case that thesemiconductor layer 21 of the TFT 20 is formed of amorphous silicon, theregion to be the channel 21 c of the semiconductor layer 21 can beformed of LTPS.

In the example in FIG. 2A, the gate electrode 23 is formed over thesubstrate 10 via a base coat layer 11, the gate insulating layer 22 andthe semiconductor layer 21 are deposited so as to cover the gateelectrode 23, the second semiconductor layer 211 is formed on thesemiconductor layer 21, and the drain electrode 26 and the sourceelectrode 25 are deposited on the second semiconductor layer 211. Thecathode wiring 27 and a second electrode 44 of the organiclight-emitting element 40 are connected via a cathode contact 44 a. Inthe example in FIG. 2B, the drain electrode 26 and the source electrode25 are formed on the base coat layer 11, the semiconductor layer 21 isdeposited on the base coat layer 11 between the drain electrode 26 andthe source electrode 25 so as to overlap with a part of the drainelectrode 26 and a part of the source electrode 25, and, moreover, thegate insulating layer 22 is deposited on the semiconductor layer 21 andthe gate electrode 23 is formed on the gate insulating layer 22.

In the example in FIG. 2C, the semiconductor layer 21 comprising asource 21 s, the region to be a channel 21 c being formed of LTPS, and adrain 21 d is formed on the base coat layer 11, and a gate insulatinglayer 22 is deposited so as to cover the semiconductor layer 21. Thegate electrode 23 is formed on the gate insulating layer 22, aninterlayer insulating layer 24 is deposited so as to cover the gateelectrode 23, and the source electrode 25 and the drain electrode 26 areformed on the interlayer insulating layer 24. The source electrode 25and the drain electrode 26 are connected to the source 21 s and thedrain 21 d, respectively, of the semiconductor layer 21 via a contacthole 24 a. The cathode contact 44 a is made up of a first contact 28penetrating the gate insulating layer 22 and the interlayer insulatinglayer 24, and a second contact 45 penetrating the planarizing layer 30.The example shown in FIGS. 2A to 2C merely differ mutually in thestructure of the TFT 20 (mainly in the vertical relationship in thelamination of constituting elements of the TFT 20). In FIGS. 2A to 2C,the same reference numerals are affixed to constituting elements havingthe same functions, so that repeated explanations of such constitutingelements will be omitted.

The organic light-emitting element 40 being a top emission-type(TE-type) organic light-emitting diode (OLED) in the examples in FIG. 2Ato 2C comprises a first electrode (for example, an anode) 41 beingformed on the planarizing layer 30, an insulating bank 42 surroundingthe first electrode 41, an organic light-emitting layer 43 being formedwithin the insulating bank 42, and a second electrode (for example, acathode) 44 being formed over the entirety of the substrate 10, such ason the organic light-emitting layer 43. In the examples in FIGS. 2A to2C, the source electrode 25 of the TFT 20 is connected to the firstelectrode 41 of the organic light-emitting element 40.

In a case that the organic light-emitting element 40 is of the TE-typeas in the examples in FIGS. 2A to 2C, the TFT 20 can be formed, at theunderlayer (between the first electrode 41 and the substrate 10) of alight-emitting region of the organic light-emitting element 40, or, inother words, a region at which the organic light-emitting layer 43 isformed, so as to overlap with a part of or the entirety of thelight-emitting region. In that case, the TFT 20 allowing a large currentto flow can be formed.

As shown in FIGS. 3A to 3C, the drain electrode 26 and the sourceelectrode 25 are made up of a conductor layer made of titanium oraluminum, for example, and a part of a first conductor layer 26 a makingup the drain electrode 26 and a part of a second conductor layer 25 amaking up the source electrode 25 are alternately lined up along a givendirection. In the example in FIG. 3A, the respective parts of theconductor layers are alternately lined up along the vertical direction(Y direction) in FIG. 3A. The region to be the channel 21 c is a regionin the semiconductor layer 21 being sandwiched between the part of thefirst conductor layer 26 a and the part of the second conductor layer 25a. As described previously, a channel is formed in the region 21 c byapplying a given voltage to the gate electrode 23, and the drainelectrode 26 and the source electrode 25 electrically conduct with eachother.

In this way, the part of the first conductor layer 26 a and the part ofthe second conductor layer 25 a are alternately lined up along a givendirection (the Y direction in FIG. 3A), therefore, it is possible toobtain a drain electrode 26 and a source electrode 25 each having a longportion at which these electrodes face each other in a region having agiven size. Therefore, a channel having a large channel width (W) can beformed. On the other hand, a channel length L being the interval betweenthe first conductor layer 26 a and the second conductor layer 25 a doesnot increase in conjunction with the part of the first conductor layer26 a and the part of the second conductor layer 25 a being alternatelylined up. Therefore, a limited region can be effectively utilized toform a channel having a large ratio (W/L) of the channel width (W) andthe channel length (L), or, in other words, a channel through which alarge current is allowed to flow. Therefore, the TFT 20 having a greatdrive capability, for example, can be formed in one pixel and a drivecircuit having a great drive capability can be formed for each pixel.

Moreover, when the part of the first conductor layer 26 a and the partof the second conductor layer 25 a are alternately lined up in this wayand a channel having a large W/L ratio is formed in a region of a givensize, it become possible to form the semiconductor layer 21 by not thepreviously-described LTPS but amorphous silicon. Describing in furtherdetail, the electron mobility in LTPS is approximately 100 cm²/Vs, whilethe electron mobility in amorphous silicon is approximately 0.5 cm²/Vs.Therefore, in a case of using amorphous silicon, the W/L ratio simplyneeds to be increased to approximately 200 times the W/L ratio(approximately 2.5, for example) of a channel using LTPS being put inpractical use. However, the electron mobility of the semiconductor layeractually needed for driving the organic light-emitting element of theorganic-EL display apparatus is approximately 10 cm²/Vs in a case of thepreviously-described W/L ratio currently used for the LTPS. Therefore,increasing the W/L ratio approximately 20 times the current W/L ratio,for example, makes it possible to use amorphous silicon for thesemiconductor layer 21 of the TFT 20 of the drive circuit 2. Therefore,for example, forming a channel having a W/L ratio of 50 or more bylining up the part of the first conductor layer 26 a and the part of thesecond conductor layer 25 a alternately makes it possible to useamorphous silicon for the semiconductor layer 21, thereby eliminatingthe need for the annealing process for obtaining LTPS as describedpreviously. In other words, the TFT 20 of the drive circuit 2 can beformed easily and inexpensively without using expensive facilities and,even more, with a method being possible to follow upsizing of the mothersubstrate. Moreover, the amorphous silicon has small variations incarrier mobility, therefore, it is possible to reduce the occurrence ofdisplay non-uniformity, and thereby, eliminating the need for a circuitfor compensating the display non-uniformity. Thus, also in light ofthese aspects, it is possible to contribute to reducing the cost of theorganic-EL display apparatus and improving the display quality.

In the example in FIG. 3A, each of the first conductor layer 26 a andthe second conductor layer 25 a is formed into a comb shape in planarview. Then, comb tooth portions (first portions 26 a 1 to 26 a 4 in theexample in FIG. 3A) of the first conductor layer 26 a and comb toothportions (second portions 25 a 1 to 25 a 4 in the example in FIG. 3A) ofthe second conductor layer 25 a are formed such that the comb toothportions of the first conductor layer 26 a engage with the comb toothportions of the second conductor layer 25 a. In the bottom gate-type TFT20 such as the example in FIG. 2A, the gate electrode 23 being shown inbroken lines in FIGS. 3A to 3C is formed below the first conductor layer26 a and the second conductor layer 25 a (between the gate insulatinglayer 22 and the substrate 10, see FIG. 4A). Moreover, in the topgate-type TFT 20 such as the example in FIG. 2B, the gate electrode 23is formed above the first conductor layer 26 a and the second conductorlayer 25 a (on the gate insulating layer 22, see FIG. 4B). The gateelectrode 23 is formed so as to overlap with a facing portions of thefirst portions 26 a 1 to 26 a 4 and the second portions 25 a 1 to 25 a 4(all of the facing portions in the example in FIG. 3A).

The gate electrode 23 is formed over the entire range of a length Wa ofa portion at which the first portions 26 a 1 to 26 a 4 being a part ofthe first conductor layer 26 a and the second portions 25 a 1 to 25 a 4being a part of the second conductor layer 25 a face each other.Therefore, a channel is formed between the second portions 25 a 1 to 25a 4 and the first portions 26 a 1 to 26 a 4 facing each other in the Ydirection in an area up to each tip of the first portions 26 a 1 to 26 a4 and the second portions 25 a 1 to 25 a 4. Moreover, in the example inFIG. 3A, the gate electrode 23 is formed such that the gate electrode 23overlaps with portions between the second conductor layer 25 and thefirst portions 26 al to 26 a 4, at which the tips of the first portions26 al to 26 a 4 face the second conductor layer 25 in a direction (Xdirection in FIG. 3A) being orthogonal to the Y direction, and such thatthe gate electrode 23 overlaps with portions between the first conductorlayer 26 and the second portions 25 a 1 to 25 a 4, at which the tips ofthe second portions 25 a 1 to 25 a 4 face the first conductor layer 26in the X direction. Therefore, a channel is formed in the entirety ofthe region 21 c between the first conductor layer 26 a and the secondconductor layer 25 a so that this region 21 c which is to be a channelhas a zigzag shape. Therefore, a channel having a large channel width(W), namely, a channel through which a large current is allowed to flowcan be formed, effectively using a limited region as exactly shown inFIG. 3A, for example.

The first portions 26 a 1 to 26 a 4 of the first conductor layer 26 aand the second portions 25 al to 25 a 4 of the second conductor layer 25a are alternately lined up along a given direction (the Y direction inFIG. 3A), so that the region to be a channel 21 c exists in a pluralityin the Y direction. Specifically, it exists in each of a regionsandwiched between the second portion 25 a 1 and the first portion 26 a1, a region sandwiched between the first portion 26 al and the secondportion 25 a 2, and a region sandwiched between the second portion 25 a2 and the first portion 26 a 2, for example, in the semiconductor layer21. In the example in FIG. 3A, the region to be a channel 21 c is anintegral (a continuous) region having a zigzag shape and a channel whichis formed in the region to be a channel 21 c preferably has the W/Lratio of 50 or more. However, in the tip portion of each of the firstportions 26 a 1 to 26 a 4 and the second portions 25 a 1 to 25 a 4, thechannel length varies at the corner.

Therefore, the channel width (W) to be used in calculating the W/L ratiois preferably set to be the total sum (Wa*n) of the length Wa ofportions at which a part (any the first portions 26 a 1 to 26 a 4) ofthe first conductor layer 26 a and a part (any of the second portions 25a 1 to 25 a 4) of the second conductor layer 25 a face each other, ineach region to be a channel 21 c existing in a plurality (for example,n) in the Y direction. Then, the ratio (W/L) of the channel width(W=Wa*n) and the interval (the channel length L) between the firstconductor layer 26 a and the second conductor layer 25 a at the portionin which a part of the first conductor layer 26 a and a part of thesecond conductor layer 25 a face each other is preferably 50 or more.The first conductor layer 26 a and the second conductor layer 25 a canbe provided in this way to surely obtain a preferable W/L ratio eventhough the channel width between the tip of each of a part of the firstconductor layer 26 a and a part of the second conductor layer 25 a, andthe second conductor layer 25 a or the first conductor layer 26 a isignored. The length Wa is a length of the facing portion of the firstand second conductor layers in a direction (the X direction) orthogonalto a direction (the Y direction) in which a part of the first conductorlayer 26 a and a part of the second conductor layer 25 a are alternatelylined up. Moreover, as shown with Wa*n, the total sum of lengths Wa is asum of lengths for all of the regions to be a channel 21 c existing in aplurality in the Y direction.

The greater the W/L ratio of the channel of the TFT 20 is, the morepreferable it is from a viewpoint of the drive capability. However, itcan also be preferable not to increase the W/L ratio more than necessaryfrom a viewpoint of the size of the thin-film transistor 20. Forexample, as described previously, the electron mobility in amorphoussilicon is approximately 1/200 of the electron mobility in LTPS, sothat, even in a case of obtaining the same drive capability as that ofthe semiconductor layer made of LTPS currently used, it suffices thatthe W/L ratio be 200 times the W/L ratio (for example, approximately2.5) of the channel made of LTPS. Therefore, the ratio (W/L) of thetotal sum (W) of lengths (Wa) of the portions at which a part of thefirst conductor layer 26 a and a part of the second conductor layer 25 aface each other in the region to be a channel 21 c, and the interval Lbetween the first conductor layer 26 a and the second conductor layer 25a is preferably 50 or more and 500 or less.

Also in the example in FIG. 3B, each of the first conductor layer 26 aand the second conductor layer 25 a is formed so as to have a comb shapein planar view. In the example in FIG. 3B, a length We of comb toothportions (first portions 26 al to 26 a 3) of the first conductor layer26 a and comb tooth portions (second portions 25 a 1 to 25 a 3) of thesecond conductor layer 25 a is greater than a length Lc of a connectionportion connecting the comb tooth portions. Moreover, a light-emittingregion 43 a of the organic light-emitting element 40 (see FIG. 2A) beingshown in a chain double-dashed line in FIG. 3B is formed in arectangular shape. Then, a portion at which the first portions 26 a 1 to26 a 3 being a part of the first conductor layer 26 a and the secondportions 25 al to 25 a 3 being a part of the second conductor layer 25 aface each other is formed along a long side of the rectangular shape ofthe light-emitting region 43 a.

Forming, in such a manner as in the example in FIG. 3B, the facingportions of each of the first conductor layer 26 a and the secondconductor layer 25 a makes it possible to increase the length Wa offacing portions to be counted in the channel width (W) in thecalculation of the previously-mentioned W/L ratio. Moreover, the numberof portions, between the tip of a part of the first conductor layer 26 aor the tip of a part of the second conductor layer 25 a and the secondconductor layer 25 a or the first conductor layer 26 a, which are notincorporated in the calculation of the W/L ratio, can be reduced. It canbe considered that the allowable current amount in the channel beingeasily calculatable and the actual allowable current amount can bebrought closer, thus making it possible to suitably design the TFT 20.It can be considered that the example in FIG. 3B be preferable in a casethat the TFT 20 is formed so as to fall in a pixel of which greatmajority is occupied by the light-emitting region 43 a having arectangular shape.

In FIG. 3C, yet another example of the first conductor layer 26 a andthe second conductor layer 25 a is shown. In the example in FIG. 3C, thefirst conductor layer 26 a is formed so as to have a zig-zag planarshape in which first portions 26 a 1 to 26 a 6 being a part of the firstconductor layer 26 a are connected at an alternately different endportion. Then, the second conductive layer 25 a is formed in thesurrounding of the first conductor layer 26 a and, further, each ofsecond portions 25 a 1 to 25 a 6 being a part of the second conductivelayer 25 a is inserted into a concavity of the zig-zag planar shape thatthe first conductor layer 26 a has. Unlike the example in FIG. 3C, thesecond conductor layer 25 a can be formed so as to have a zig-zag planarshape, while a part of the first conductor layer 26 a can be insertedinto a concavity of the planar-shape of the second conductor layer 25 a.As exemplified in FIG. 3C, the first conductor layer 26 a and the secondconductor layer 25 a do not necessarily have to be formed so as to havea comb tooth-shape as in the examples in FIGS. 3A and 3B. Moreover, thenumber of first portions of the first conductor layer 26 a and thenumber of second portions of the second conductor layer 25 a isconstrued to be not limited to the examples in FIGS. 3A to 3C, so thatan arbitrary number of first portions and second portions can beprovided. Except for the planar shape of the first and second conductorlayers 26 a, 25 a, the TFT 20 shown in FIGS. 3B and 3C is the same asthe TFT 20 shown in FIG. 3A, so that repeated explanations will beomitted.

FIGS. 4A and 4B show cross-sectional views along a cutting line beingparallel to the X direction and passing through the first portion 26 a 1of the first conductor layer 26 a shown in FIG. 3A. Unlike the examplein FIG. 3A, FIGS. 4A and 4B are examples in which the gate electrode 23is provided in a width being smaller than the length Wa of the facingportion of a part of the first conductor layer 26 a and a part of thesecond conductor layer 25 a. FIG. 4A is an example in which the TFT 20is of a bottom gate-type, while FIG. 4B is an example in which the TFT20 is of a top gate-type. In other words, in FIG. 4A, the gate electrode23, the gate insulating layer 22, the semiconductor layer 21, and thefirst conductor layer 26 a being deposited over the substrate 10 via thebase coat layer are formed in reverse order to those in FIG. 4B. Ineither one of FIGS. 4A and 4B, the tip of the first portion 26 a 1 ofthe first conductive layer 26 a and the second conductive layer 25 a areseparated by a distance Lx. The distance Lx is generally equal to theinterval between the first conductor layer 26 a and the second conductorlayer 25 a facing each other along a direction (the Y direction shown inFIG. 3A) in which a part of the first conductor layer 26 a and a part ofthe second conductive layer 25 a are alternately lined up, for example.

With reference to FIGS. 2A to 2C again, constituting elements other thanthe TFT 20 of the organic-EL display apparatus 1 will be described. Theplanarizing layer 30 comprises a first inorganic insulating layer 31being deposited on the drive circuit 2, an organic insulating layer 32being deposited on the first inorganic insulating layer 31, and a secondinorganic insulating layer 33 being deposited on the organic insulatinglayer 32. A surface of the planarizing layer 30 facing to an oppositeorientation from the drive circuit 2 (a surface of the second inorganicinsulating layer 33 facing to an opposite orientation from the organicinsulating layer 32) has an arithmetic average roughness of 50 nm orless. In other words, according to the organic-EL display apparatus 1according to the present embodiment, the surface of the substrate 10having unevenness due to forming the drive circuit 2 is covered by theplanarizing layer 30, and the surface of the planarizing layer 30 isformed to 50 nm or less in arithmetic average roughness (Ra). Forexample, the planarizing layer 30 can be formed to 50 nm or less inarithmetic average roughness by being polished after depositing of eachinsulating layer.

As described previously, as a result of the present inventors havingmade studies on the cause that display non-uniformity is produced in theorganic-EL display apparatus, it was found that the surface of theorganic light-emitting layer in the organic light-emitting element isnot a completely planar surface, but comprises a minute unevenness,having a microscopically inclined portion. The surface of the organiclight-emitting layer being inclined causes the normal direction of thesurface of the organic light-emitting layer to incline relative to thenormal direction of the display surface of the organic-EL displayapparatus. In such a case, it becomes difficult to recognize a lightemitted in the slanted direction from such an organic light-emittinglayer from the front of the display surface. Therefore, deterioration inluminance, or variation in chromaticity determined by the intensity oflight of each color of R, G, and B occurred.

Conventionally, a circuit was added to each drive circuit provided foreach pixel to compensate for the characteristic variations of the TFTand/or the OLED, for example, as measures for the displaynon-uniformity. However, these measures did not effectively function asmeasures for the display non-uniformity found by the present inventors,but rather could increase unevenness of the surface of the substratewith an increase in the number of constituting elements of the drivecircuit. Moreover, currents to pass through individual organiclight-emitting elements could be controlled based on the luminancedistribution grasped by the inspection process of the organic-EL displayapparatus. However, these measures caused the cost and size to increasein conjunction with an increase in the number of constituting elementsof the drive circuit, complication of the manufacturing process of theorganic-EL display apparatus, or complicated control to be needed.

On the other hand, in the present embodiment, as described previously,in order to eliminate the newly found cause of display non-uniformity,the surface of the planarizing layer 30 is brought to the arithmeticaverage roughness of 50 nm or less. Moreover, the organic light-emittinglayer 43 is formed avoiding the position directly above a contact hole30 a to be described below. In this way, a display image having anextremely small display non-uniformity can be obtained. While thesurface roughness of the planarizing layer 30 being smaller is morepreferable, the arithmetic average roughness being such as to be set asa target in the polishing process in the semiconductor process, forexample, to be less than 20 nm, is not necessarily required. In otherwords, the present inventors have found that, from a viewpoint ofsuppressing the display non-uniformity of the organic-EL displayapparatus 1, it suffices that the surface of the planarizing layer 30has the arithmetic average roughness of 50 nm or less, in which case thedisplay non-uniformity such as to be detected by a human being is seldomproduced. Moreover, it has been found that the arithmetic averageroughness of 20 nm or more is preferable from the aspect of the ease ofimplementation. In other words, in view of coping with both easymanufacture and effective suppression of the display non-uniformity thatcan influence the display quality, it is preferable that the surface ofthe planarizing layer 30 having the arithmetic average roughness of 20nm or more and 50 nm or less.

For the substrate 10, a glass substrate or a polyimide layer is mainlyused. In a case that the organic-EL display apparatus 1 is of a bottomemission-type (BE-type) unlike the examples in FIGS. 2A to 2C, alight-transmitting material, or, in other words, a glass substrate, atransparent polyimide film, or the like can be used. The base coat layer11 is formed as a barrier layer on the surface of the substrate 10 onwhich the TFT 20 is formed. For example, using plasma CVD, the base coatlayer 11 is formed having an underlayer mainly comprising an SiO₂ layerhaving a thickness of approximately 500 nm and an SiN_(X) layer having athickness of approximately 50 nm, and an overlayer mainly comprising anSiO₂ layer having a thickness of approximately 250 nm.

The drive circuit 2 comprising the TFT 20 is formed over the base coatlayer 11. The cathode wiring 27 is also formed over the base coat layer11. While being omitted in FIG. 2A, wirings for scanning lines and datalines are also formed in the same manner as the cathode wiring 27.Moreover, while only the TFT 20 to drive the light-emitting element 40is shown in FIG. 2A, the previously-described switching TFT 2 a is alsoformed on the base coat layer 11, and other TFTs can also be formedthereon. In a case that the organic-EL display apparatus 1 is of theTE-type as the example in FIG. 2A, the drive circuit 2 can be formedacross the entire surface below a light-emitting region of the organiclight-emitting element 40. On the other hand, with the BE-type, the TFT20 cannot be formed below the light-emitting region of the organiclight-emitting element 40, so that the TFT 20 is formed at theperipheral edge of a portion overlapping in planar view with thelight-emitting region. However, even in this case, the planarizing layer30 is required that has, at the surface thereof, the planarity of such adegree as to not produce the display non-uniformity.

The gate insulating layer 22 of the TFT 20 mainly comprises SiO₂ ofapproximately 50 nm in thickness, while the gate electrode 23 is formedby patterning after forming a layer of Mo, for example, of approximately250 nm in thickness.

A first inorganic insulating layer 31 comprising SiN_(X) ofapproximately 200 nm in thickness is formed as a barrier layer on thesurface of the drive circuit 2 comprising the TFT 20, an organicinsulating layer 32 is formed over the first inorganic insulating layer31, and a second inorganic insulating layer 33 is formed thereover. Inthe planarizing layer 30, the contact hole 30 a is formed, whichcollectively penetrates the first inorganic insulating layer 31, theorganic insulating layer 32, and the second inorganic insulating layer33. As described below, a metal such as indium tin oxide (ITO), andsilver (Ag), or APC (silver, copper and palladium), for example, isembedded into the contact hole 30 a, and the drive circuit 2 and theorganic light-emitting element 40 are connected to each other via thismetal.

The organic insulating layer 32 has a thickness of approximately 1 μm ormore and 2 μm or less, for example. The unevenness of the surface of thesubstrate 10 due to forming of the drive circuit 2 is substantiallyreduced by the organic insulating layer 32. The organic insulating layer32 is formed using a polyimide resin or an acrylic resin, for example.Moreover, the organic insulating layer 32 preferably comprises anadditive agent (a leveling improving agent) to improve the planarity ofthe surface of the organic insulating layer 32 facing the secondinorganic insulating layer 33, at the content of 0.5 mass % or more and5.0 mass % or less. Examples of such a leveling improving agent includesilicone-based, hydrocarbon-based, and fluorine-based surfactants.Moreover, while the organic insulating layer 32 can be formed using aphotosensitive resin, a photopolymerization initiator can reduce theeffect of the leveling improving agent, so that a material notcomprising a photosensitive body such as a photopolymerization initiatoris preferably used for the organic insulating layer 32.

The acrylic resin is high in purity, fits well with a surfactant, andhas a high planarity, so that it is preferable as a material for theorganic insulating layer 32. On the other hand, in a case that themanufacturing process of the organic-EL display apparatus 1 comprises aprocess of high temperature of 200° C. or more, a polyimide resin havinga high heat resistance is preferable. Therefore, the organic insulatinglayer 32 is preferably an acrylic resin not comprising a photosensitivebody such as a photopolymerization initiator, or a polyimide resin notcomprising the photosensitive body.

The second inorganic insulating layer 33 has the arithmetic averageroughness of 50 nm or less at the surface facing to the oppositeorientation from the organic insulating layer 32 as describedpreviously, therefore, the display non-uniformity of the organic-ELdisplay apparatus 1 can be suppressed. While the second inorganicinsulating layer 33 is formed of SiN_(X) or SiO₂, for example, SiN_(X)is preferable in terms of barrier properties to moisture. In otherwords, the barrier performance to moisture of the planarizing layer 30is improved by the second inorganic insulating layer 33.

The second inorganic insulating layer 33 can also have an effect ofblocking moisture at the time of not only use of but also manufacturingof the organic-EL display apparatus 1. In other words, as describedbelow, the surface of the planarizing layer 30 can be polished in themanufacturing process so as to have the surface roughness of 50 nm orless and cleaning can be carried out to remove the polishing agent afterpolishing. In a case that the second inorganic insulating layer 33 isnot formed, the surface of the organic insulating layer 32 is to bepolished and further to be exposed to the cleaning agent. In that case,the cleaning agent can penetrate into the organic insulating layer 32,remain as it is, and cause deterioration of the TFT 20. However, by thesecond inorganic insulating layer 33 being formed, such a penetration ofthe cleaning agent into the organic insulating layer 32 and such adeterioration of the TFT 20 can be prevented.

The second inorganic insulating layer 33 is formed so as to have thethickness of approximately 100 nm or more and 600 nm or less, forexample. However, the thickness of the second inorganic insulating layer33 varies based on the unevenness of the surface of the organicinsulating layer 32 facing to the second inorganic insulating layer 33.The second inorganic insulating layer 33 is preferably formed so as tohave a thickness of equal to or more than three times a maximum heightdifference DT of the unevenness of the surface of the organic insulatinglayer 32, for example, such that the unevenness of the surface of theorganic insulating layer 32 can be sufficiently embedded in the secondinorganic insulating layer 33. Then, it is preferable that the surfaceof the second inorganic insulating layer 33 be polished, as needed, forthe length (the thickness) of equal to or more than maximum heightdifference DT and less than two times the maximum height difference DT.In this way, without exposing the organic insulating layer 32, it ispossible to trim the protrusion of the surface of the second inorganicinsulating layer 33 due to the protrusion of the surface of the organicinsulating layer 32 and the surface of the planarizing layer 30 can bealmost certainly brought to the arithmetic average roughness of 50 nm orless. In that case, over the entirety of the surface of organicinsulating layer 32, the second inorganic insulating layer 33 can havethe thickness of equal to or more than one times the maximum heightdifference DT and equal to or less than three times the maximum heightdifference DT of the unevenness of the surface of the organic insulatinglayer 32. For example, in FIG. 2A, a maximum thickness TL of the secondinorganic insulating layer 33 is equal to or more than two times themaximum height difference DT and equal to or less than three times themaximum height difference DT of the unevenness of the organic insulatinglayer 32, while a minimum thickness TM of the second inorganicinsulating layer 33 is equal to or more than one times the maximumheight difference DT and equal to or less than two times the maximumheight difference DT of the unevenness of the organic insulating layer32. In particular, in the example in FIG. 2A, the maximum thickness TLof the second inorganic insulating layer 33 is substantially two timesthe maximum height difference DT of the unevenness of the organicinsulating layer 32, while the minimum thickness TM of the secondinorganic insulating layer 33 is substantially the same as the maximumheight difference DT of the unevenness of the organic insulating layer32.

The first electrode 41 of the organic light-emitting element 40 isformed integrally with the metal being embedded into the contact hole 30a. In other words, ITO, a metal such as Ag or APC, and ITO are embeddedinto the contact hole 30 a using sputtering, for example, and an ITOlayer, a metal layer such as Ag layer or APC layer, and an ITO layerwhich are composed of the same substances as the inside of the contacthole 30 are also formed on the surface of the planarizing layer 30.These are patterned to a given shape, so that the first electrode 41 isformed. However, as described previously, the region at which theorganic light-emitting layer 43 is formed is set so as to avoid theposition directly above the contact hole 30 a. In relation to theorganic light-emitting layer 43, the first electrode 41 preferably has awork function of approximately 5 eV, so that, in a case of the topemission-type, ITO, and Ag or APC as described previously are used. TheITO layer is formed so as to have the thickness of approximately 10 nm,while the Ag or APC layer is formed so as to have the thickness ofapproximately 100 nm. In a case of the bottom emission-type, only theITO layer having the thickness of approximately 300 nm or more and 1 μmor less is formed, for example. In the planarizing layer 30, a contacthole 30 b to form the cathode contact 44 a is also formed, and thecontact hole 30 b also collectively penetrates each insulating layermaking up the planarizing layer 30.

In a portion directly above the contact hole 30 a of the surface of thefirst electrode 41 can be produced a hollow as shown in FIG. 2A in acase that the contact hole 30 a is not completely filled with ITO.However, in the example in FIG. 2A, the first electrode 41 has a regionnot overlapping in planar view with the contact hole 30 a at a sizebeing sufficient to form the organic light-emitting layer 43, and theorganic light-emitting layer 43 is formed at the region not overlappingwith the contact hole 30 a. Therefore, the non-uniformity of thicknessof the organic light-emitting layer 43 and the hollow at the surfacethereof is unlikely to be produced, and the display non-uniformitycaused by the contact hole 30 a is unlikely to be produced.

The insulating bank 42 to insulate the first electrode 41 from thesecond electrode 44 as well as to demarcate each pixel is formed at theperipheral edge of the first electrode 41. In the example in FIG. 2A,the hollow of the surface of the first electrode 41 is covered with theinsulating bank 42. Then, the organic light-emitting layer 43 isdeposited on the first electrode 41 being surrounded by the insulatingbank 42. The organic light-emitting layer 43 to be a light-emittingregion of the organic light-emitting element 40 is formed preferably ata region not overlapping in planar view with the contact hole 30 a as inthe example in FIG. 2A. In that case, as described previously, thedisplay non-uniformity caused by the contact hole 30 a is unlikely to beproduced. While the organic light-emitting layer 43 is shown as onelayer in FIG. 1, it is formed as a plurality of organic layers bydepositing various materials. The organic light-emitting layer 43 isformed by printing, or vapor deposition in which an organic materialbeing evaporated or sublimed is selectively adhered onto only a requiredportion using a mask.

As a layer to be in contact with the first electrode 41, for example, apositive hole injection layer is provided, which comprises a materialhaving a high compatibility with ionization energy to improve theinjectability of positive holes. A positive hole transport layerallowing trapping of electrons into the light-emitting layer (as theenergy barrier) as well as improving the stable transport of positiveholes is formed by an amine-based material, for example, on the positivehole injection layer. Moreover, the light-emitting layer is formed onthe positive hole transport layer, which is selected in accordance witha wavelength of light to be emitted. For example, an organicluminescence material of red or green is doped to Alq₃ for red or green,for example. Moreover, as a blue-color material, a DSA-based organicmaterial is used. Furthermore, on the light-emitting layer, an electrontransport layer to stably transport electrons as well as to improve theinjectability of electrons is formed by Alq₃. These individual layers,each having a thickness of approximately several tens of nm, aredeposited to form a deposited organic light-emitting layer 43. Anelectron injection layer made of, for example, LiF or Liq to improve theinjectability of electrons can be provided between the organiclight-emitting layer 43 and the second electrode 44.

The second electrode 44 is formed over the organic light-emitting layer43. In the examples in FIG. 2A to 2C, the second electrode 44 iscontinuously formed so as to be common across all the pixels, and isconnected to the cathode wiring 27 via the cathode contact 44 a formedin the planarizing layer 30. The second electrode 44 is formed by alight-transmitting material, for example, a thin-film Mg—Ag layer. Forthe second electrode 44, a material having a small work function ispreferable, so that an alkaline metal, or an alkaline earth metal can beused. Mg (magnesium) is preferable in having a small work function of3.6 eV, and Ag having a small work function of approximately 4.25 eV isco-vapor deposited at the ratio of approximately 10 mass % to providestability. With the BE-type, the second electrode 44 is a reflectingplate, so that Al (aluminum) is thickly deposited as the secondelectrode 44.

An encapsulation layer (TFE) 46 to prevent moisture from reaching to thesecond electrode 44 is formed over the second electrode 44. Theencapsulation layer 46, comprising an inorganic insulating layer such asSiN_(X) or SiO₂, for example, is formed by forming a single-depositedfilm, or two or more layers of deposited film. For example, two layersof deposited film in which the thickness of each layer is approximatelybetween 0.1 μm and 0.5 μm are formed as the encapsulation layer 46. Theencapsulation layer 46 is preferably formed in a multilayer usingdifferent materials so as to obtain sufficient barrier property withrespect to moisture even when a pin hole is created in one layer. Theencapsulation layer 46 is formed such as to completely coat the organiclight-emitting layer 43 and the second electrode 44. The encapsulationlayer 46 can comprise an organic insulating layer in between two layersof inorganic insulating layer.

(Method of Manufacturing an Organic-EL Display Apparatus)

Herein below, with the organic-EL display apparatus 1 shown in FIG. 2Aas an example, a method of manufacturing an organic-EL display apparatusaccording to one embodiment is explained with reference to flowcharts inFIGS. 5A and 5B and cross-sectional views shown in FIGS. 6A to 6G andalso with reference to FIG. 3A as needed.

As shown in FIG. 6A, a drive circuit 2 comprising a thin-film transistor20 is formed on a substrate 10 (S1 in FIG. 5A).

In a case that the organic-EL display apparatus 1 shown in FIG. 2A ismanufactured, a base coat layer 11 is formed on the surface of thesubstrate 10 using plasma CVD, for example. While the base coat layer 11is shown with a single layer structure in FIG. 6A, it is formed, forexample, by depositing an SiO₂ layer having a thickness of approximately500 nm, an SiN_(X) layer having a thickness of approximately 50 nm onthe SiO₂ layer, and further an SiO₂ layer having a thickness ofapproximately 250 nm on the SiN_(X) layer.

Thereafter, a gate electrode 23 is formed by forming a metal layer suchas Mo layer using sputtering, for example, and patterning the metallayer (S11 in FIG. 5B). Preferably, along with the gate electrode 23, acathode wiring 27 and each wiring (not shown) for other lines such asscanning lines and data lines can be formed. For example, as shown inthe FIG. 3A previously referred to, the gate electrode 23 extending in agiven direction (Y direction in the example in FIG. 3A) in which a partof the first conductor layer 26 a and a part of the second conductorlayer 25 a are alternately lined up is formed.

A gate insulating layer 22 is formed on the gate electrode 23 (S12 inFIG. 5B). The gate insulating layer 22 is formed by forming an SiO₂layer or an SiN_(X) layer having a thickness of approximately 50 nmusing plasma CVD, for example. Moreover, a semiconductor layer 21 madeup of amorphous silicon is formed on the gate insulating layer 22, usingplasma CVD, for example, such that the semiconductor layer 21 covers thegate electrode 23 (S13 in FIG. 5B). A dehydrogenation process on thesemiconductor layer 21 is carried out by annealing for approximately 45minutes under the temperature of approximately 350° C., for example. Thesemiconductor layer 21 is patterned into a desired shape using, forexample, dry etching. As described previously, in a case that the gateelectrode 23 extends in a given direction in which a part of the firstconductor layer 26 a and a part of the second conductor layer 25 a arealternately lined up, the semiconductor layer 21 extending along thegiven direction to cover the entire gate electrode 23 is formed.

Thereafter, a second semiconductor layer 211 having a high impurityconcentration is preferably formed at a region on the semiconductorlayer 21, on which the first conductor layer 26 a or the secondconductor layer 25 a is to be formed later (S14 in FIG. 5B). In otherwords, interposing the second semiconductor layer 211 having a highimpurity concentration between the semiconductor layer 21 and each ofthe first conductor layer 26 a and the second conductor layer 25 a ispreferable in reducing the contact resistance between the semiconductorlayer 21, and a drain electrode 26 and a source electrode 25. The secondsemiconductor layer 211 can be formed on the semiconductor layer 21 bydepositing a semiconductor layer having an impurity concentration higherthan that of the semiconductor layer 21, or it can be formed by dopingimpurities into a given region of the semiconductor layer 21. Asimpurities, phosphorus or arsenic can be exemplified in a case that theTFT 20 is a N-channel field-effect transistor, while boron or aluminumcan be exemplified in a case that the TFT 20 is a P-channel field-effecttransistor.

The first conductor layer 26 a making up the drain electrode 26 and thesecond conductor layer 25 a making up the source electrode 25 are formedon the semiconductor layer 21 (or the second semiconductor layer 211)and the gate insulating layer 22 (S15 in FIG. 5B). For example, atitanium layer or an aluminum layer each having a thickness of severalhundreds of nm, or a deposited layer thereof is formed using sputtering.Then, by dry etching, for example, the formed metal layer is separatedinto the first conductor layer 26 a and the second conductor layer 25 a,and unneeded portions are removed. As a result, the first conductorlayer 26 a comprising a plurality of first portions (four first portions26 a 1 to 26 a 4 in the example in FIG. 3A) extending along a direction(the X direction in FIG. 3A, for example) crossing a given direction(the Y direction in FIG. 3A, for example) is formed. At the same time,the second conductor layer 25 a comprising a plurality of secondportions (four second portions 25 a 1 to 25 a 4 in the example in FIG.3A) extending along a direction crossing the given direction (the Ydirection in FIG. 3A) is formed. The first conductive layer 26 a and thesecond conductor layer 25 a are formed such that each of the pluralityof first portions and each of the plurality of second portions arealternately arranged along the given direction (the Y direction in FIG.3A). As a result, the TFT 20 is formed over the substrate 10. As shownin FIG. 6A, the TFT 20 is formed so as to have a deposition structure ofthe gate electrode 23, the gate insulating layer 22, the semiconductorlayer 21, the first conductor layer 26 a making up the drain electrode26, and the second conductor layer 25 a making up the source electrode25. Moreover, as exemplified in FIG. 3A, the first conductor layer 26and the second conductor layer 25 are formed such that a part of eachthereof is alternately lined up along the given direction. And thesemiconductor layer 21 comprises a region to be a channel 21 c being aregion sandwiched between a part of the first conductor layer 26 a and apart of the second conductor layer 25 a.

Each of the first conductor layer 26 a and the second conductor layer 25a can be formed so as to have a comb shape in planar view as in theexample in FIG. 3A. Also, the first conductor layer 26 a and the secondconductor layer 25 a can be formed such that comb tooth portions (thefirst portions 26 a 1 to 26 a 4 in the example in FIG. 3A) of the firstconductor layer 26 a and comb tooth portions (the second portions 25 a 1to 25 a 4 in the example in FIG. 3A) of the second conductor layer 25 aengage with each other.

In a case that the top gate-type TFT 20 as exemplified in FIG. 2B isformed, each constituting element is formed using generally the samemethod as that for forming the bottom gate-type TFT 20 as exemplified inFIG. 2A, but in a procedure being generally reverse to the proceduredescribed above. In other words, first, the first conductor layer 26 acomprising a plurality of first portions (four first portions 26 a 1 to26 a 4 in the example in FIG. 3A) extending along a direction (the Xdirection in FIG. 3A, for example) crossing a given direction (the Ydirection shown in FIG. 3A, for example) is formed on the substrate 10.Moreover, along with the first conductor layer 26 a being formed, thesecond conductor layer 25 a comprising a plurality of second portions(four second portions 25 a 1 to 25 a 4 in the example in FIG. 3A)extending along a direction crossing the given direction (the Ydirection in FIG. 3A) is formed. The first conductor layer 26 a and thesecond conductor layer 25 a are formed such that each of the pluralityof first portions and each of the plurality of second portions arealternately arranged along the given direction (the Y direction in FIG.3A).

Thereafter, the semiconductor layer 21 made of amorphous silicon isformed on the first conductor layer 26 a and the second conductor layer25 a. Preferably, a semiconductor layer 21 is formed, which extendsalong the given direction in which each of the plurality of firstportions of the first conductor layer 26 a and each of the plurality ofsecond portions of the second conductor layer 25 a are alternatelyarranged. Then, the gate insulating layer 22 is formed on thesemiconductor layer 21 and the gate electrode 23 is formed, on the gateinsulating layer 22, so as to cover a portion at which the first portionof the first conductor layer 26 a and the second portion of the secondconductor layer 25 a face each other. Preferably, a gate electrode 23 isformed, which extends along the given direction in which each of theplurality of first portions of the first conductor layer 26 a and eachof the plurality of second portions of the second conductor layer 25 aare alternately lined up.

Moreover, in a case that the top gate-type TFT 20 being exemplified inFIG. 2C is formed, the semiconductor layer 21, the gate insulating layer22, the gate electrode 23, an interlayer insulating layer 24, the drainelectrode 26 (the first conductor layer 26 a), and the source electrode25 (the second conductor layer 25 a) are formed in order over thesubstrate 10. An excimer laser is irradiated to the semiconductor layer21 and amorphous silicon is converted into polysilicon (LTPS) by such anannealing. Moreover, impurity ions are doped into regions to be a source21 s and a drain 21 d in the semiconductor layer 21. Contact holes 24 aare formed by, for example, dry etching in the interlayer insulatinglayer 24 and the gate insulating layer 22, and filed up with a metal atthe time of forming the drain electrode 26 and the source electrode 25.

Thereafter, as shown in FIG. 6B, a first inorganic insulating layer 31,an organic insulating layer 32, and a second inorganic insulating layer33 are formed (S2 in FIG. 5A) on the surface of the drive circuit 2 (seeFIG. 6A). The first inorganic insulating layer 31 is formed by forming alayer of, for example, SiN_(X) or SiO₂ having a thickness ofapproximately 200 nm using plasma CVD, for example. The organicinsulating layer 32 is formed by applying a liquid resin or a pastyresin of low viscosity. Slit coating or spin coating, and slit and spincoating in which both thereof are combined can be exemplified as methodsof applying. The organic insulating layer 32 is formed so as to have athickness of approximately 1 μm or more and 2 μm or less. As a materialfor the organic insulating layer 32, a polyimide resin or an acrylicresin can be used, for example. A non-photosensitive resin notcomprising the photosensitive body is preferable in that it is high inpurity and, even more, the surface smoothness of the organic insulatinglayer 32 is high. Particularly, the acrylic resin is preferable.

The second inorganic insulating layer 33 is formed by forming a layerconsisting of, for example, SiN_(X) or SiO₂ using plasma CVD, forexample, in the same manner as forming the first inorganic insulatinglayer 31. Forming the second inorganic insulating layer 33 makes itpossible to prevent penetration, into the organic insulating layer 32,of various solvents such as a cleaning agent that can be used in apost-process, and the possibly-resulting deterioration of the TFT 20.

The second inorganic insulating layer 33 is preferably formed so as tohave a thickness to be selected based on a maximum height difference DTof the unevenness of the surface of the organic insulating layer 32. Forexample, the second inorganic insulating layer 33 is formed so as tohave a thickness equal to or more than twice the maximum heightdifference DT of the unevenness of a surface of the organic insulatinglayer 32 facing to the second inorganic insulating layer 33. This makesit possible to ensure that a recess on the surface of the organicinsulating layer 32 be filled by a part of the second inorganicinsulating layer 33. Moreover, the second inorganic insulating layer 33is more preferably formed so as to have a thickness of equal to or morethan two times the maximum height difference DT and equal to or lessthan three times the maximum height difference DT of the unevenness ofthe surface of the organic insulating layer 32. This makes it possibleto surely fill the recess of the organic insulating layer 32 asdescribed previously. Moreover, in the below-described polishingprocess, it is possible, without unnecessarily thickening the secondinorganic insulating layer 33, to certainly level the unevenness that isbased on the unevenness of the organic insulating layer 32 and canappear on the surface of the second inorganic insulation layer 33 afterformation thereof. Even more, it is possible to almost certainly preventthe organic insulating layer 32 from being exposed after the polishing.

Next, as shown in FIG. 6C, the surface of the second inorganicinsulating layer 33 is polished (S3 in FIG. 5A). It has been found bythe present inventors that, as described previously, in a case that thesurface of the planarizing layer 30 to be the base for an organiclight-emitting element 40 (see FIG. 2A) is not sufficiently planar, thedisplay non-uniformity can be produced in the organic-EL displayapparatus. Therefore, the surface of the second inorganic insulatinglayer 33 being the surface of the planarizing layer 30 is polished. Thesurface of the second inorganic insulating layer 33 is preferablypolished so as to have an arithmetic average roughness of 50 nm or less.Polishing the surface to the surface roughness of such a degree and,moreover, forming an organic light-emitting layer 43 avoiding theposition directly above the contact hole 30 a as described later make itpossible to ensure that a display non-uniformity such as to be detectedby a human being be seldom produced as described previously. Moreover,in planarization of the surface of the planarizing layer 30, thearithmetic average roughness such as to be set as a target in thesemiconductor process is not necessarily required. Rather, in order toavoid a complicated and time-consuming polishing process including aninspection of the surface roughness, the surface of the second inorganicinsulating layer 33 is preferably polished so as to have an arithmeticaverage roughness of 20 nm or more and 50 nm or less.

In polishing of the surface of the second inorganic insulating layer 33,the second inorganic insulating layer 33 is polished such that thepolishing amount (the amount of decrease in thickness of the secondinorganic insulating layer 33 due to polishing) at least partiallyreaches an amount equal to or more than one times the maximum heightdifference DT and less than two times the maximum height difference DTof the unevenness of the surface of the organic insulating layer 32. Inthis way, in a case that the second inorganic insulating layer 33 isformed so as to have the thickness of equal to or more than twice themaximum height difference DT of the unevenness of the organic insulatinglayer 32 as described previously, unevenness that can appear on thesurface of the second inorganic insulating layer 33 after formationthereof based on the unevenness of the organic insulating layer 32 cansurely be leveled. Even more, it is possible to almost certainly preventthe exposure of the organic insulating layer 32 due to polishing. Forexample, in the example in FIG. 6C, a polishing amount P1 in a region(for example, a region in which the TFT 20 is formed) being a protrusionat the surface of the second inorganic insulating layer 33 afterformation thereof is around twice the maximum height difference DT ofthe unevenness at the surface of the organic insulating layer 32.Moreover, in the example in FIG. 6C, a polishing amount P2 in a region(for example, a region in which the TFT 20 is not formed) being a recessat the surface of the second inorganic insulating layer 33 afterformation thereof is an amount being substantially the same as butslightly below the maximum height difference DT of the unevenness of theorganic insulating layer 32.

Method of polishing the second inorganic insulating layer 33 is notparticularly limited. However, in order to achieve the arithmeticaverage roughness of 50 nm or less, polishing is preferably carried outby CMP (chemical mechanical polishing) in which a neutral slurrycontaining cerium, colloidal silica, or fumed silica is used as apolishing agent. The CMP makes it possible to increase the effect ofmechanical polishing through surface chemical action which the polishingagent has, for example, and to rapidly obtain a smoothly polishedsurface. Cerium can be an effective polishing agent for the secondinorganic insulating layer 33 being formed of SiO₂ since Cerium has highhardness and a Ceria (CeO₂) being an oxide of Cerium causes a chemicalreaction with glass. Colloidal silica refers to a colloidal hydratedSiO₂ or colloidal SiO₂ normally having the particle diameter of 10 nm to300 nm, while fumed silica (also called a dry silica or ahighly-dispersed silica) refers to spherical SiO₂ particles having theparticle diameter of 10 nm to 30 nm being aggregated (the particlediameter of 100 nm to 400 nm), and both thereof effectively function aspolishing agents.

Moreover, for polishing of the second inorganic insulating layer 33,neutral aqueous alcohol or potassium hydroxide aqueous solution is usedtogether with the previously-described polishing agent. In particular,in a case that the substrate 10 is formed of a polyimide resin, from aviewpoint of preventing corrosion of the substrate 10, the surface ofthe second inorganic insulating layer 33 is preferably polished usingthe neutral alcohol solution together with the previously-describedpolishing agent.

As shown in FIG. 6D, a contact hole 30 a is formed (S4 in FIG. 5A) inthe second inorganic insulating layer 33, the organic insulating layer32, and the first inorganic insulating layer 31, so as to reach thedrive circuit 2 (see FIG. 6A). Preferably, the contact hole 30 a tocollectively penetrate these three insulating layers is formed. Thecontact hole 30 a is preferably formed at a region not overlapping, inthe thickness direction of the substrate 10, with a region at which anorganic light-emitting layer 43 (see FIG. 6F) is to be formed in aformation of the organic light-emitting layer 43 to be described below.This makes it possible to prevent the occurrence of displaynon-uniformity as described previously. Forming of the contact hole 30 ais carried out using dry etching after a resist mask is formed, forexample. At the time of forming the contact hole 30 a, the contact hole30 b for a cathode contact 44 a (see FIG. 2A) is formed also in aportion above the cathode wiring 27 of the planarizing layer 30.

As shown in FIG. 6E, a metal is embedded at the interior of the contacthole 30 a and a first electrode 41 of the organic light-emitting element40 (see FIG. 2A) is formed in a given region (S5 of FIG. 5A). Morespecifically, using sputtering, for example, an underlayer in which aredeposited an ITO layer having a thickness of approximately 10 nm, and anAg layer or an APC layer having a thickness of approximately 100 nm, andan overlayer mainly comprising an ITO layer having a thickness ofapproximately 10 nm are formed. As a result, a deposited layerconsisting of the ITO layer, the Ag layer or the APC layer, and the ITOlayer is formed on the surface of the planarizing layer 30 as well asthe metal is embedded at the interior of the contact hole 30 a.Thereafter, the deposited layer is patterned to form the first electrode41. As shown in FIG. 6E, this deposited layer is preferably patternedsuch that the first electrode 41 has a region having a sufficient sizewith respect to forming of the organic light-emitting layer 43 and notoverlapping with the contact hole 30 a in planar view. At the time ofembedding the metal into the contact hole 30 a, the contact hole 30 b isfilled at least with the ITO layer, and the Ag layer or APC layer, sothat the cathode contact 44 a is formed.

As shown in FIG. 6F, the organic light-emitting layer 43 is formed onthe first electrode 41 (S6 in FIG. 5A). Specifically, an insulating bank42 is formed at the peripheral edge of the first electrode 41. Theinsulating bank 42 can be an inorganic insulating layer such as SiO₂, oran organic insulating layer such as a polyimide resin or an acrylicresin. For example, such an insulating layer is formed on the entiresurface of the first electrode 41 and the planarizing layer 30 and agiven region of the first electrode 41 is exposed by the patterning theformed insulation layer. Preferably, a region of the first electrode 41,which does not overlap with the contact hole 30 a in the thicknessdirection of the substrate 10 is exposed. The insulating bank 42 isformed so as to have a height of approximately 1 μm. As describedpreviously, various organic materials are deposited in forming of theorganic light-emitting layer 43. Depositing of the organic material iscarried out by vacuum vapor deposition, for example, in which case theorganic material is vapor-deposited via a vapor-deposition mask havingan aperture corresponding to a desired pixel, such as R, G, or B. Alayer such as LiF to improve the injectability of electrons can beformed on the surface of the organic light-emitting layer 43. Theorganic light-emitting layer 43 can be formed by inkjet printing, notvapor deposition.

As shown in FIG. 6G, a second electrode 44 is formed on the organiclight-emitting layer 43 (S7 in FIG. 5A). The second electrode 44 isformed by forming a thin-film of Mg—Ag eutectic film using co-vapordeposition, for example. The second electrode 44 is formed also on thecathode contact 44 a and connected to the cathode wiring 27 via thecathode contact 44 a. The Mg—Ag eutectic film comprises Mg atapproximately 90 mass % and Ag at approximately 10 mass %, for example.The second electrode 44 is formed so as to have a thickness ofapproximately 10 to 20 nm, for example.

An encapsulation layer 46 (see FIG. 2A) to protect the second electrode44 and the organic light-emitting layer 43 from, for example, moistureor oxygen is formed over the second electrode 44. The encapsulationlayer 46 is formed by forming, using plasma CVD, an inorganic insulatinglayer such as SiO₂ or SiN_(X). The encapsulation layer 46 is preferablyformed such that the end portion thereof comes into close contact withan inorganic layer such as the second inorganic insulating layer 33.This is because joining of the inorganic layers together causes them tobe joined in close contact with each other. This makes it possible tomore surely prevent penetration of moisture. The organic-EL displayapparatus 1 shown in FIG. 2A can be manufactured by undergoing theabove-described process.

SUMMARY

(1) An organic-EL display apparatus according to first embodiment of thepresent invention comprises: a substrate having a surface with a drivecircuit formed on the surface, the drive circuit comprising a thin-filmtransistor; a planarizing layer to planarize the surface of thesubstrate by covering the drive circuit; and an organic light-emittingelement being formed on a surface of the planarizing layer facing to anopposite orientation from the drive circuit, and electrically connectedto the drive circuit, wherein the surface of the planarizing layer hasan arithmetic average roughness of 50 nm or less; the thin-filmtransistor comprises a gate electrode, a drain electrode, a sourceelectrode, and a semiconductor layer comprising a region to be a channelof the thin-film transistor and partially overlapping with the drainelectrode and the source electrode; a part of a first conductor layermaking up the drain electrode and a part of a second conductor layermaking up the source electrode are alternately lined up along a givendirection; and the region to be a channel is sandwiched between the partof the first conductor layer and the part of the second conductor layer.

The configuration according to (1) makes it possible to enhance thecapability of a drive circuit with a structure also allowing realizationof cost reduction and, even more, to reduce display non-uniformity in anorganic-EL display apparatus.

(2) In the organic-EL display apparatus according to (1) mentionedabove, the semiconductor layer can comprise a plurality of regions, eachone of the plurality of regions being the region to be a channel beingsandwiched between the part of the first conductor layer and the part ofthe second conductor layer, the semiconductor layer can be made ofamorphous silicon, and W/L can be 50 or more and 500 or less, whereinthe W denotes a sum of lengths of facing portions in the plurality ofregions, each of the facing portions being a portion at which the partof the first conductor layer and the part of the second conductor layerface each other, and the L denotes an interval between the firstconductor layer and the second conductor layer at the facing portions.In that case, a drive circuit having a high current-drive capability canbe formed.

(3) In the organic-EL display apparatus according to (1) or (2)mentioned above, each of the first conductor layer and the secondconductor layer can be formed into a comb shape in planar view and canbe formed such that a comb tooth portion of the first conductor layerand a comb tooth portion of the second conductor layer engage with eachother. In that case, a large number of facing portions of the part ofthe first conductor layer and the part of the second conductor layer canbe efficiently formed.

(4) In the organic-EL display apparatus according to any one of (1) to(3) mentioned above, a light-emitting region of the organiclight-emitting element can be formed in a rectangular shape, thethin-film transistor can be formed at an underlayer of thelight-emitting region, and a portion at which the part of the firstconductor layer and the part of the second conductor layer face eachother can be formed along a long side of the rectangular shape. In thatcase, a TFT having a large channel width, able to fall into a pixel or alight-emitting region of a rectangular shape, and having a propertybeing close to the design value can be obtained.

(5) In the organic-EL display apparatus according to any one of (1) to(4) mentioned above, the gate electrode can be formed over an entirerange of a length of a portion at which the part of the first conductorlayer and the part of the second conductor layer face each other. Inthat case, a TFT having a large channel width including the entirelength of the portion at which the first conductor layer and the secondconductor layer face each other.

(6) In the organic-EL display apparatus according to any one of (1) to(5) mentioned above, the planarizing layer can comprise a firstinorganic insulating layer being deposited on the drive circuit; anorganic insulating layer being deposited on the first inorganicinsulating layer; and a second inorganic insulating layer beingdeposited on the organic insulating layer, and a surface of the secondinorganic insulating layer facing to an opposite orientation from theorganic insulating layer can have a surface roughness of 20 nm or moreand 50 nm or less. In that case, it can be easily achieved to cope withboth easy manufacture and effective suppression of the displaynon-uniformity that can influence the display quality.

(7) In the organic-EL display apparatus according to (6) mentionedabove, a thickness of the second inorganic insulating layer can varybased on an unevenness of a surface of the organic insulating layerfacing to the second inorganic insulating layer, and the thickness ofthe second inorganic insulating layer can be equal to or more than onetimes a maximum height difference of the unevenness and equal to or lessthan three times the maximum height difference of the unevenness over anentirety of the surface of the organic insulating layer. In that case,the organic insulating layer is never exposed, and the unevenness of thesurface of the organic insulating layer can be leveled at the surface ofthe planarizing layer.

(8) A method of manufacturing an organic-EL display apparatus accordingto second embodiment of the present invention comprises: forming a drivecircuit on a substrate, the drive circuit comprising a thin-filmtransistor; forming, on a surface of the drive circuit, a firstinorganic insulating layer, an organic insulating layer, and a secondinorganic insulating layer; polishing a surface of the second inorganicinsulating layer; forming a contact hole in the second inorganicinsulating layer, the organic insulating layer, and the first inorganicinsulating layer, so as to reach the thin-film transistor; embedding ametal at the interior of the contact hole and forming a first electrodeat a given region; forming an organic light-emitting layer on the firstelectrode; and forming a second electrode on the organic light-emittinglayer, wherein the thin-film transistor is formed so as to have adeposition structure comprising a gate electrode, a gate insulatinglayer, a semiconductor layer comprising a region to be a channel, afirst conductor layer making up a drain electrode, and a secondconductor layer making up a source electrode; the first conductor layerand the second conductor layer are formed such that a part of the firstconductor layer and a part of the second conductor layer are alternatelylined up along a given direction; and the region to be a channel issandwiched between the part of the first conductor layer and the part ofthe second conductor layer.

The configuration according to (8) makes it possible to suitablymanufacture an organic-EL display apparatus having a drive circuit beingexcellent in drive capability and having a small display non-uniformity.

(9) In the method of manufacturing an organic-EL display apparatusaccording to (8) mentioned above, forming the thin-film transistor cancomprise: forming, on the substrate, the gate electrode extending alongthe given direction; forming the gate insulating layer on the gateelectrode; forming, on the gate insulating layer, the semiconductorlayer made of amorphous silicon and extending along the given direction,so as to cover the gate electrode; and forming the first conductor layercomprising a plurality of first portions extending along a directioncrossing the given direction and the second conductor layer comprising aplurality of second portions extending along a direction crossing thegiven direction such that the each first portion and each second portionare alternately arranged along the given direction. This makes itpossible to form a TFT having a bottom gate structure (reverse-staggeredstructure).

(10) In the method of manufacturing an organic-EL display apparatusaccording to (8) mentioned above, forming the thin-film transistor cancomprise: forming, on the substrate, the first conductor layercomprising a plurality of first portions extending along a directioncrossing the given direction and the second conductor layer comprising aplurality of second portions extending along a direction crossing thegiven direction such that each first portion and each second portion arealternately arranged along the given direction; forming thesemiconductor layer made of amorphous silicon and extending along thegiven direction, on the first conductor layer and the second conductorlayer; forming the gate insulating layer on the semiconductor layer; andforming, on the gate insulating layer, the gate electrode extendingalong the given direction, so as to cover a portion at which each firstportion and each second portion face each other. This makes it possibleto form a TFT of a top gate structure (staggered structure).

(11) In the method of manufacturing an organic-EL display apparatusaccording to any one of (8) to (10) mentioned above, each of the firstconductor layer and the second conductor layer can be formed so as tohave a comb shape and can be formed such that a comb tooth portion ofthe first conductor layer and a comb tooth portion of the secondconductor layer engage with each other. In this way, a large number offacing portions of the part of the first conductor layer and the part ofthe second conductor layer can be formed efficiently.

(12) In the method of manufacturing an organic-EL display apparatusaccording to any one of (8) to (11) mentioned above, a secondsemiconductor layer having a high impurity concentration can beinterposed between the semiconductor layer and each of the firstconductor layer and the second conductor layer. This makes it possibleto reduce the contact resistance between the semiconductor layer andeach of the drain electrode and the source electrode.

(13) In the method of manufacturing an organic-EL display apparatusaccording to (8) to (12) mentioned above, in forming of the secondinorganic insulating layer, the second inorganic insulating layer can beformed so as to have a thickness of equal to or more than twice amaximum height difference of an unevenness of a surface of the organicinsulating layer; and, in polishing of the surface of the secondinorganic insulating layer, the second inorganic insulating layer can bepolished such that an amount of decrease in a thickness of the secondinorganic insulating layer due to the polishing reaches, at leastpartially, an amount equal to or more than one times the maximum heightdifference and less than two times the maximum height difference. Inthis way, the unevenness that can appear on the surface of the secondinorganic insulating layer after formation thereof based on theunevenness of the organic insulating layer can surely be leveled, and,even more, exposure of the organic insulating layer due to the polishingcan almost surely be prevented.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 Organic-EL display apparatus    -   2 Drive circuit    -   3 Organic-EL display panel    -   10 Substrate    -   20 Thin-film transistor (driving TFT, TFT)    -   21 Semiconductor layer    -   21 c Region to be a channel    -   22 Gate insulating layer    -   23 Gate electrode    -   25 Source electrode    -   25 a Second conductor layer    -   25 a 1 to 25 a 6 Second portions (comb tooth portions)    -   26 Drain electrode    -   26 a First conductor layer    -   26 a 1 to 26 a 6 First portions (comb tooth portions)    -   30 Planarizing layer    -   30 a, 30 b Contact hole    -   31 First inorganic insulating layer    -   32 Organic insulating layer    -   33 Second inorganic insulating layer    -   40 Organic light-emitting element (OLED)    -   41 First electrode    -   43 Organic light-emitting layer    -   44 Second electrode

1. An organic-electroluminescent (EL) display apparatus, comprising: asubstrate having a surface with a drive circuit formed on the surface,the drive circuit being formed for each of pixels and comprising athin-film transistor; a planarizing layer to planarize the surface ofthe substrate by covering the drive circuit; and an organiclight-emitting element being formed, for each of the pixels, on asurface of the planarizing layer facing to an opposite orientation fromthe drive circuit, the organic light-emitting element being electricallyconnected to the drive circuit, wherein the thin-film transistorcomprises a gate electrode, a drain electrode, a source electrode, and asemiconductor layer comprising a region to be a channel of the thin-filmtransistor and partially overlapping with the drain electrode and thesource electrode; a part of a first conductor layer making up the drainelectrode and a part of a second conductor layer making up the sourceelectrode are alternately lined up along a given direction; a pluralityof regions each one of which is the region to be the channel is providedand each of the regions is sandwiched between the part of the firstconductor layer and the part of the second conductor layer; and W/L is50 or more and 500 or less, wherein the W denotes a sum of lengths offacing portions in the plurality of regions, each of the facing portionsbeing a portion at which the part of the first conductor layer and thepart of the second conductor layer face each other, and the L denotes aninterval between the first conductor layer and the second conductorlayer at the facing portions.
 2. The organic-EL display apparatusaccording to claim 1, wherein each of the thin-film transistors isformed under a light-emitting region of each of the organiclight-emitting elements, so as to overlap with an entirety of thelight-emitting region.
 3. The organic-EL display apparatus according toclaim 1, wherein a light-emitting region of each of the organiclight-emitting elements is formed in a rectangular shape; the thin-filmtransistor is formed at an underlayer of the light-emitting region; thepart of the first conductor layer and the part of the second conductorlayer extend along a long side of the rectangular shape; a length of thepart of the first conductor layer, which extends along the long side isgreater than a length of a connection portion connecting a plurality ofthe parts of the first conductor layer; and a length of the part of thesecond conductor layer, which extends along the long side is greaterthan a length of a connection portion connecting a plurality of theparts of the second conductor layer.
 4. The organic-EL display apparatusaccording to claim 1, wherein plural parts each being the part of one ofthe first conductor layer and the second conductor layer are coupled atrespective end portions, and thereby the one of the first conductorlayer and the second conductor layer has a zig-zag planer shape; otherone of the first conductor layer and the second conductor layer isformed at surroundings of the one of the first conductor layer and thesecond conductor layer; and the part of the other one of the firstconductor layer and the second conductor layer is inserted into aconcavity of the zig-zag planer shape.
 5. The organic-EL displayapparatus according to claim 1, wherein the planarizing layer comprisesa first inorganic insulating layer being deposited on the drive circuit,an organic insulating layer being deposited on the first inorganicinsulating layer, and a second inorganic insulating layer beingdeposited on the organic insulating layer; and the organic insulatinglayer comprises an additive agent at a content rate of 0.5 mass % ormore and 5 mass % or less, wherein the additive agent improves aplanarity of a surface of the organic insulating layer facing to thesecond inorganic insulating layer.
 6. The organic-EL display apparatusaccording to claim 1, wherein the planarizing layer comprises a firstinorganic insulating layer being deposited on the drive circuit, anorganic insulating layer being deposited on the first inorganicinsulating layer, and a second inorganic insulating layer beingdeposited on the organic insulating layer; a thickness of the secondinorganic insulating layer varies based on an unevenness of a surface ofthe organic insulating layer facing to the second inorganic insulatinglayer; a maximum thickness of the second inorganic insulating layer isequal to or more than two times a maximum height difference of theunevenness and equal to or less than three times the maximum heightdifference of the unevenness, and a minimum thickness of the secondinorganic insulating layer is equal to or more than one times themaximum height difference of the unevenness and equal to or less thantwo times the maximum height difference of the unevenness.
 7. Anorganic-electroluminescent (EL) display apparatus, comprising: asubstrate having a surface with a drive circuit formed on the surface,the drive circuit being formed for each of pixels and comprising athin-film transistor; a planarizing layer to planarize the surface ofthe substrate by covering the drive circuit; and an organiclight-emitting element being formed, for each of the pixels, on asurface of the planarizing layer facing to an opposite orientation fromthe drive circuit, the organic light-emitting element being electricallyconnected to the drive circuit, wherein the thin-film transistorcomprises a gate electrode, a drain electrode, a source electrode, and asemiconductor layer comprising a region to be a channel of the thin-filmtransistor and partially overlapping with the drain electrode and thesource electrode; a part of a first conductor layer making up the drainelectrode and a part of a second conductor layer making up the sourceelectrode are alternately lined up along a given direction; a pluralityof regions each one of which is the region to be the channel is providedand each of the regions is sandwiched between the part of the firstconductor layer and the part of the second conductor layer; plural partseach being the part of one of the first conductor layer and the secondconductor layer are coupled at respective end portions, and thereby theone of the first conductor layer and the second conductor layer has azig-zag planer shape; other one of the first conductor layer and thesecond conductor layer is formed at surroundings of the one of the firstconductor layer and the second conductor layer; and the part of theother one of the first conductor layer and the second conductor layer isinserted into a concavity of the zig-zag planer shape.
 8. The organic-ELdisplay apparatus according to claim 7, wherein each of the thin-filmtransistors is formed under a light-emitting region of each of theorganic light-emitting elements, so as to overlap with an entirety ofthe light-emitting region.
 9. The organic-EL display apparatus accordingto claim 7, wherein the planarizing layer comprises a first inorganicinsulating layer being deposited on the drive circuit, an organicinsulating layer being deposited on the first inorganic insulatinglayer, and a second inorganic insulating layer being deposited on theorganic insulating layer; and the organic insulating layer comprises anadditive agent at a content rate of 0.5 mass % or more and 5 mass % orless, wherein the additive agent improves a planarity of a surface ofthe organic insulating layer facing to the second inorganic insulatinglayer.
 10. The organic-EL display apparatus according to claim 7,wherein the planarizing layer comprises a first inorganic insulatinglayer being deposited on the drive circuit, an organic insulating layerbeing deposited on the first inorganic insulating layer, and a secondinorganic insulating layer being deposited on the organic insulatinglayer; a thickness of the second inorganic insulating layer varies basedon an unevenness of a surface of the organic insulating layer facing tothe second inorganic insulating layer; a maximum thickness of the secondinorganic insulating layer is equal to or more than two times a maximumheight difference of the unevenness and equal to or less than threetimes the maximum height difference of the unevenness, and a minimumthickness of the second inorganic insulating layer is equal to or morethan one times the maximum height difference of the unevenness and equalto or less than two times the maximum height difference of theunevenness.
 11. A method of manufacturing an organic-electroluminescent(EL) display apparatus, the method comprising: forming, on a substrate,a drive circuit for each of pixels, the drive circuit comprising athin-film transistor; forming, on a surface of the drive circuit, afirst inorganic insulating layer, an organic insulating layer, and asecond inorganic insulating layer; forming a contact hole in the secondinorganic insulating layer, the organic insulating layer, and the firstinorganic insulating layer, so as to reach the thin-film transistor;embedding a metal at an interior of the contact hole, forming a firstelectrode at a given region for each of the pixels, forming an organiclight-emitting layer on the first electrode, and forming a secondelectrode on the organic light-emitting layer, thereby forming anorganic light-emitting element, wherein the thin-film transistor isformed so as to have a deposition structure comprising a gate electrode,a gate insulating layer, a semiconductor layer comprising a region to bea channel, a first conductor layer making up a drain electrode, and asecond conductor layer making up a source electrode; the first conductorlayer and the second conductor layer are formed such that a part of thefirst conductor layer and a part of the second conductor layer arealternately lined up along a given direction; a plurality of regionseach one of which is the region to be the channel is provided and eachof the regions is sandwiched between the part of the first conductorlayer and the part of the second conductor layer; and W/L is 50 or moreand 500 or less, wherein the W denotes a sum of lengths of facingportions in the plurality of regions, each of the facing portions beinga portion at which the part of the first conductor layer and the part ofthe second conductor layer face each other, and the L denotes aninterval between the first conductor layer and the second conductorlayer at the facing portions.
 12. The method of manufacturing theorganic-EL display apparatus according to claim 11, wherein each of thethin-film transistors is formed under a light-emitting region at whicheach of the organic light-emitting layer is formed, so as to overlapwith an entirety of the light-emitting region.